Conventionally, manufacturers must produce dozens of correspondingly shaped roll pairs due to the diversification of the dimensions of the middle soles. Applicant's U.S. patent application Ser. No. 08/133,620 disclosed a middle sole sloping machine including a pair of rolls respectively incorporating a spring so that the lengths and heights of which can be adjusted. Applicant's U.S. patent application Ser. No. 08/292,493 provided an improved design to give an automatic control for such adjustment.
Although the Applicant's above said two prior inventions are proved to be able to function well, they still need an improvement concerning the rolls.
Refer to FIGS. 9 and 10 which respectively show a pair of rolls for the Applicant's said two prior inventions and a middle sole 62 obtained by cutting a blank 60 rolled by the prior rolls. The pair of rolls include an upper roll 80 and a lower roll 90. The upper roll 80 includes a left roll section 81, a right roll section 82 and a spring 83 connected therebetween. Similarly, the lower roll 90 includes a left roll section 91, a right roll section 92 and a spring 93 connected therebetween. When the rolls 80 and 90 are rotated to roll the blank 60 for production of the middle sole 62, since each of the springs 83, 93 is formed by a plurality of continuous coils, the pressure points for which each spring exerts a pressure on the blank 60 will be laterally shifted following the passing of the blank 60 through the rolls 80, 90. Such a shift of pressure points will cause the rolled blank 60 to be irregularly laterally extended, which, in turn, will result in that the middle sole 62 (FIG. 10) obtained by cutting the rolled blank 60 will also have an irregular shape, rather than a generally rectangular shape. Such an irregular shape of the middle sole 62 will adversely affect the quality of the shoe incorporating the middle sole 62.
The present invention is disclosed to improve the structure of the pair of rolls to mitigate and/or obviate the above-mentioned problems concerning the Applicant's '620 and '493 patent applications.